1. Field of the Invention
This invention is related to growth of Group III nitride materials, and in particular to a method of heteroepitaxial growth of high quality, Nitrogen (N) face Gallium Nitride (GaN), Indium Nitride (InN), Aluminum Nitride (AlN), and their alloys, by Metal Organic Chemical Vapor Deposition (MOCVD).
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
The use of group III nitride materials in consumer applications and devices is becoming widespread. However, the majority of applications employ Ga-polar group-III nitride films and heterostructures. Films and heterostructures of the opposite polarity (N-polar group-III nitride films and heterostructures) have been much less investigated due to difficulties in their growth. N-polar group-III nitride films and heterostructures are advantageous for the fabrication of a variety of nitride based electronic and optoelectronic devices. The opposite direction of the piezoelectric fields in N-polar heterostructures, in comparison to Ga-polar heterostructures, allows the fabrication of transistor devices which cannot be fabricated using Ga-polar heterostructures.
One of the major challenges to III-Nitride based light emitters is the growth of high quality InGaN with high In composition. The use of the Gallium (Ga)-face for devices limits the temperature at which the InGaN can be grown, which limits the types of devices that can be made. Another challenge is the growth of low resistance p-type (Al,Ga,In)N:Mg films due to polarity conversion from Ga-face to N-face at high Mg doping levels. By using N-face (Al,Ga,In)N layer structures both issues can be mitigated.
The opposite direction of the piezoelectric fields in N-polar in comparison to Ga-polar heterostructures leads to a lower operating voltage of Light Emitting Diodes (LEDs) and Laser Diodes (LDs), and to improved carrier injection in p-n junction devices, due to a narrower width of the depletion region in general. Furthermore, the opposite direction of the piezolelectric fields has advantages for devices such as transistors, solar cells and devices utilizing tunnel junctions. It can be seen that there is a need in the art for N-face nitride materials and methods to grow these materials.